Olefins are conventionally produced through the process of steam or catalytic cracking of various hydrocarbons. Olefins can also be produced by catalytically converting oxygenates to olefin compounds. The olefin product of such processes includes numerous olefin components (i.e., compounds), as well as certain non-olefin components, which have to be separated for further conversion to other chemical compounds such as olefin dimers, oligomers or polymers.
Conventional processes for separating olefin streams into other olefin component streams include compressing the olefin stream prior to separation into the other component streams. These processes typically involve multi-stage compression processes, which require several large compressors, and the compressed olefin stream is cooled after each stage with intercoolers.
U.S. Pat. No. 6,444,869 discloses one type of process for the separation and recovery of ethylene and heavier components from an oxygenate conversion process. The oxygenate conversion effluent stream, which comprises hydrogen, carbon dioxide, water, C2 to C4 hydrocarbons and oxygenates, is withdrawn from the oxygenate conversion reactor and passed to a multi-stage effluent compressor to raise the pressure of the oxygenate conversion effluent stream to provide a compressed effluent stream. The compressed effluent stream is passed to an oxygenate removal zone for the recovery of various oxygenates to provide an oxygenate depleted effluent stream. The oxygenate depleted effluent stream is passed to a carbon dioxide removal zone, and then to a dryer zone. The dry effluent is passed to a series of fractionation zones to separate the individual olefins into high purity products.
U.S. Pat. No. 6,441,261 discloses making an olefin stream by contacting oxygenate with a molecular sieve catalyst, compressing the olefin stream, and separating olefin components from the olefin stream. The olefin product stream is compressed in a compressor comprising one to four stages with cooling of the material between stages (intercooling). Higher compression ratios are considered to be desirable in that they result in less expensive compression modules, but are generally limited to the extent that contaminants present in the olefin stream can cause fouling at high temperatures. However, oxygenate conversion processes are considered to provide far fewer fouling contaminants, meaning that higher compression ratios can be achieved.
Improved processes for separating olefin streams into other olefin streams containing various olefin components are desired. In particular, processes which minimize compressor fouling or reducing the number of compressor stages used in separating olefin components in an olefin stream are sought.